Electrically heated tool



March 19, 1935.

L. N. HAMPTON ELECTRICALLY HEATED ATool.

Filed Aug. 5, 1931 MN mm SN .R O

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w wv Nv ov a. O O 4 Q i ArmR/VEV Patented Mar. 19, 1935 ELECTRICALLY HEATED TOOL Leon N. Hampton, New

York, N. Y., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York `VApplication August '5,

' `6 Claims.

'Ihis invention relates to electrically heated tools and more specifically to that class of tools known as electric soldering coppers.

The object of this invention is to improve the construction and efficiency of such tools.

The features-and advantages of this tool will appear from the following description and by the claims appended thereto, reference being made to the accompanying drawing in which:

Fig. 1 is an assembly view vof theA soldering copper shown partly in section;

' Fig. 2 is an enlarged longitudinal sectional view of the heating element embodied in this soldering Copper;

Fig. 3 is an enlarged longitudinal view ofv the handle showing the switching mechanism;

Fig. 4 is a sectional view taken approximately on line 4-4 of Fig. 3;

Fig. 5 is a sectional view taken. approximately on line 5-5 of Fig. 3; land Fig. 6 is a detail -view of the switch operating knob.`

As shown in Fig. 1 the heat applying member is made of bimetal consisting of a copper portion 11 and a silver portion l2, the silver portion having a chamfered edge 13 and a threaded portion 14 for engagement with a similarly threaded bushing 15 having a beveled seat for receiving the chamfered edge of the silver portion 12. Bushing 15 like the portion 12 of the heat applying member is made of silver or any other metal having a similarly high thermal conductivity and non-corrosive characteristic in order to form a good heat path toward the copper portion of the heat applying tip and to prevent the so-called freezing of these parts as it frequently occurs in ordinary soldering copper due to` oxidation, and therefore avoiding the liability of damaging these parts upon the removal of the soldering tip from the bushing while at the ksame time improving the efilciency of the device.

Bushing 15 is secured at its front end in an enlarged portion of a supporting shell I6 made of non-corrosive material such as for example an alloy 'of chromium metal steel commercially known as Enduros. This bushing is held in the shell by a number of rivets 17 and for a dis-l tance of about two-thirds of its length cooperates with the'shell 16 to forman annular air space/18 for thermally insulating the supportingshell V16 and preventing the dissipation of the heat to the atmosphe'regfrom the bushing 15, thus forcing the heat toward the heat applying member or tip 11.

1931, Serial N0. 555,174

consists of a core 19 of a non-oxidizable material such as Monel metal which is highly efficient thermally as compared to Lavite and other insulating material heretofore used and does not corrode and scale at soldering temperature. This' core is coated with an insulating oxide at a temperature of about 2000 F. and around the core 19 isWrapped a strip of insulating material 20 such as mica on which the nichrome resistance wire 21 is coiled'in a non-inductive manner. The loop en d of the resistance wire 21 engages a lug 22 formed at the periphery of a ring 23 of lavite material mounted on the front end of the core, the ends of the nichrome Wire at the other end being inserted in slots in the periphery of a lavite -bead 24.

To the front end of the core 19 there is welded a silver bushing or ycap 25 having a flange portion 26 for engaging the core. A shoulder portion 27 is provided in the cap 25 for receiving the end of a sleeve 28 also made of silver and this sleeve is welded to the cap 25.

T'he sleeve 28'is thermally and electrically insulated from the resistance wire 21 by an annular layer 29 of insulating material as for example, .magnesium oxide. The ends of wire 21 thread through metallic sleeves 30 and 31 supported by a plurality of mica washers 32, and a lavite bead 33 in turn lmounted in the sleeve 28 and a packing 34' of magnesium oxide is placed between the b ead 24 and the mica washer 32 as shown in Fig. 2.

The end of sleeve 28 adjacent the bead 33 is then spun over the edge of this bead in order to form a selfcontained unit'and the diameter of the sleeve 28 is then reduced, as by swaging, in order to obtain a dense insulating coating around the resistance wire and at the same time denuding the magnesium oxide of gaseous substance to prevent tne oxidation and the consen quent burning of the resistancewire. The annular air space formed by the reduced portion of sleeve 28 with the bushing 15 further assists in the heat insulation `of the supporting shell 16.

On the protruding ends of bushings 30 and 31 there is mounted an insulating bead 34 of Laviteprovided for holding the wires 35 and 36 in coaxial alignment with the ends of the resistance wire 2l with which these wires connect as shownM in Fig. 2.

The supporting shell 16 has a'reduced portion in which is mounted a series of ceramic beads such as 3'1. These beads are of a diameter as to form with the inner diameter of the shell an annular air space and are provided with radial fins parlarmi OFFICE l 38. The reduced portion of shell 16 isprovided with a series of holes 39 to permit the dissipation of any heat which may reach these beads and this portion of the shell, thus forming an air 5 path from the open ends of the annular spaces formed by the sleeve portion of bushing 15 with the heating element and the supporting shell 18.

The supporting shell 16 is provided with a double convex collar portion 40, one face of which is provided with radial grooves 41 for assisting in the dissipation of the heat from the shell, and the other face is provided with two parallel at portions. 42 and 43 to be engaged by a wrench in the ordinary manner for securing the shell in a handle 44 .through the engagement of the threaded portion 45 at the end of the shell 16 with a similarly threaded metal insert 46 anchored in the handle 44, the grooved face of the double convex member 40 serving as a stop.

20 against the front end of the metal insert 46.

The wires 35 and 36 thread through parallel holes 47, Fig. 2, in the ceramic beads 37 and are connected to terminals 48 and 49 secured lto a mounting block 50 of insulating material by a screw y51 and a stud 52 the latter being placed at the center of the block 50.

A slipring 53 is held in place on theother face of this block by a screw 54 and the screw`5l, the latter electrically connecting terminal 48 with the slip ring 53. The stud 52 ise mounted on an insulating washer 55 also secured to the block 50 by the screws 51 and 54. The insulating block 50 is provided with a counter-sunk hole 56 in which is mounted a contact member 57. lIfhis contact is held in contacting relation with a coaxially disposed contact 58 by a spring 59. Con- -tact 58 is anchored in amounting block 60 of insulating material and in this block is anchored a contact member 61 disposed in contact relation with the slip ring 53 and to each of the contacting members 58 and 6l is secured one end of wires 62 and 63 by screws 64 and 65 respectively.

The insulating block 60 which is made preferably of molded phenol plastic composition material, is formed with a hook portion 66 for engagingva similarly shaped portion 67 in a plate 68 which is fastened to a frame I69 of a switching device SD by lugs 70 and 7l riveted to this frame. On this plate lis insulatively mounted two switch blades 72 and 73. To blade 73 is attached the other end of wire 63v and to blade 72 is attached one end of wire 74 of the current supply circuit, the wire 62 of the supply circuit being connected directly to thevcontact member 58 as above described.

Onframe 69 is pivotally mounted a lever member 75 which carries at its free en d a substantially U-shaped contacting member 76 arrangedto engage the switch blades 72 and 73 and thereby establishing electrical connection between the wires 63 and 74.

Lever member 75 is actuated by a sectorshaped piece 77 shown in Figs. 1, 3, 5 and 6 lplv-- oted as at 78 in the frame 69. The movement of sector 77 and the arm 79 carried therebyis effective to tension a spring 80 while moving one of its ends past the pivotal point ofV lever where the spring is caused to detent and move 70` the bridge piece 76 in contacting relation with the blades 72 and 73.

The frame 69 is provided' at its free end with a` two lugs 82 and 83 supported by an insulation block 84. The block 84 fits the inner diameter of the handle 44 and is provided with peripheral grooves 85 and 86 for holding the wires 62 and '14 in spaced relation at that point. A spring 87 'which has one end in' abutment against the block 84 and the other end against the end piece 88 of handle v44 is provided for holding the frame 69 against axial movement in the handle.

The electrical circuit for the heating element is as follows. From the supply wire 62, the screw 64, the contact member 58 engaging the plunger 57, the spring 59, thestud 52, terminal 49 and the wire 36 which connects with one end of the resistance wire 21.' The return side of the circuit is through the wire 35, terminal .48, the screw' 51, the slip ring 53, the contactmember v61, the

attaching screw 65,'the wire 63 attached to switchI ment of the bridge piece 76' from the switch blades'72 and 73 through the operation'of the actuating sector member as above described. lOn the operating knob 77 is4 provided a reference point 88 of a color different 'from that of the body portion'of the knob for visually indicating the closed and open position of the knob.

The comparatively. high degree of eiiiciency obtained in the electric soldering copper of this invention isv due in part to the use of semi-precious metal for a number of parts ofthe heating element including a portionof the soldering tip, and through the proper thermal and electrical insulation of the parts; Due to the high emciency obtained, it has been found that the heating element may be operated at a lower temperature than is practiced in ordinary soldering cop per at present in the market, which results in longer life'ofthe heating element, and in the retardation of the deterioration rate ofthe instrument. Further, it-has been found that the soldering tip becomes hotter in relation to .the shell than otherwise would be the case and that the supporting shell and the handle are cooler in proportion. The hotter tip is desirable from a-soldering standpoint. The cooler shell offers greater protection against searing or scorching of adjacent material during soldering and the cooler handle makes the copper more comfortable to handle and prolongs the life of the handle. f

The use of `semi-precious metal in the heating element and soldering tip also prevents scaling and oxidation of the parts and therefore prevents the gradual falling off ineiiiciency with the attendant increase in the temperature of the shell and in the handle and the so-called freezing of the soldering tip with its supporting bushing at the screw threads of these parts thus avoiding the liability of damaging these partsupon the removal of the soldering tip from. the

bushing. i

A switch which is placed in the handle aords a convenient means for controlling .the operation of the heating element, while its operating knob, which protrudes only slightly above the surface of the handle, does not interfere in any way with the practical handling of the instrument.

What is claimed is:

1. In an electric soldering tool, a bimetallic heat applying means consisting ofcopper and silver, the silver part having a threaded portion, a supporting shell, a silver bushing mounted in a heating element for said means mounted in said bushing, said bushing extending over the whole length of said heating element, said bushing and said heating element having portions of their outer diameters reduced to form a plural. ity of concentric air spaces for heat insulating said shell from said element.

, 2. In an electrically heated tool, the combination with a heat applying means and a tubular support, a heating velement for said means, a`

bushing mounted in said support for engaging said means, and having a portion extending over said heating element in spaced concentric relation therewith, said element comprising a core, a' strip of insulating material wrapped around said core, a resistance wire coiled around said insulation, a metallic protective shell, magnesium oxide interposed between said shell, said wire and a plurality of means at each end of said shell for-insulatively supporting said core and a metallic cap secured to the 'front end of said metallic shell and forming an abutting wall for the last mentioned means. 1

' 3. An electrically heated tool comprising a tubular support, a heating element mounted in e one end of said support, a handle mounted at the other end of said support, a switching device in said handle for controlling the operation of said element, a pair of wires in' said support connected at one end to said element, an insulating block `mounted in said tubular support, having contacts connected to the other ends of said wires, another insulating block in said support carried by said switch and having contacts engaging the contacts in the rst mentioned block and current supply circuit wires connected to said switching device and the last mentioned block. f

4. An electric soldering tool comprising a supporting shell, a bushing mounted in one end of said shell, a bimetallic heat applying means consisting of a copper part andia silver part, the silver part 'having a screw threaded portion engaging said bushing, a heating element ior said means mounted in said bushing, said element;

end to form with 'said ,supporting shell another air space open at one end, air openings ink said shell connecting said air spaces with thel atmosphere for cooling said shell and a handle secured at the other end ot said shell.

5. In an electric soldering tool, a supporting shell, a bimetallic heat applying means, one part of said means'being silver and the other part copper secured to each other, a silver bushing having a threaded portion and a sleeve portion, the silver part of said means having portions intertting said bushing, a heating element for said means mounted in said sleeve portion, said sleeve portion extending in concentric and spaced relation with said shell and said element to form therewith a plurality of air spaces for heat insulating said shell from said element, .a handle at the other end ot said shell, a switching device in said handle for controlling the operation of said heating element and insulating plugs in said supporting shell, one carried by said switching device and having engageable contacts connecting said switching device to said heating element. l

6. An electrically heated tool comprising a tubular support, a bushing having areduced sleeve portion mountedin vone end of said support, the sleeve portion forming an annular air space open at one end thereof, a heat applying means engaging said bushing, a. heating element `mounted in the sleeve portion of said bushing in end-to-end abutting relationy with said heat applying means, a cone portion carried by said support, a handle mounted on the other end of said support in abutting relation with said cone portion, a switching device mounted in said handle, a two-position rotatable sectormember protruding at one point from said handle for operating said device, electrical connections in said support extending from said device to said element, said connections including a pair of detachably mounted plugs having end-to-end en-' gageable cc'ntacts, a plurality ofl means for electrically an"1 thermally insulating said connections from said support, said sector 'member in' one position causing the operation of said element and when rotated in the yother position breaking saidconnections, and means for indi-l LEON N. HAMPTON.

eating said positions. 

